The influence of selected factors on the muscle fibre diameter according to the sexual classification of slaughter cattle [Vliv zvolených faktorů na sílu svalových vláken podle pohlavní příslušnosti jatečného skotu]

The aim of this study was to evaluate the muscle fibre diameter of bulls (n = 136),heifers (n = 38) and steers (n = 18). The influence of age at slaughter,weight at slaughter,net daily weight gain,SEUROP meatiness and SEUROP fatness on the muscle fibre diameter was observed. The group of animals included Czech Red Pied and its crossbreeds (F1) with the specialized meat breeds (Charolais and Galloway),further crossbreeds of hybrid bulls. Bulls were slaughtered at an average age of 587 days and average weight of 610 kg. The average age of heifers was 644 days and average weight at slaughter was 550 kg. The highest average age was that of steers (689 days) and they were fattened to the average weight of 610 kg. The sample of musculus longissimus lumborum et thoracis (m.l.th.) was used for the analyses. The results showed that the muscle fibres were stronger in diameter in the negatively selected (culled) heifers (p gt; 0.01) as compared to the category of bulls and steers. Apart from sex we also analysed the effect of age at slaughter of the individual animal categories on the fibre diameter. We discovered that the diameter of the fibre increased with age. The fibre diameter of bulls of up to 530 days of age was 37.86μm and at the age of more than 601 days it was 39.81μm. The diameter of the muscle fibres was also affected by the pre-slaughter weight. At lower weights the fibres of all categories of cattle were finer. Of growth factors affecting the fibre diameter we selected the net weight gain which is the general indicator of the life-long growth intensity and carcass yield. The fibre diameter in bulls and steers increased insignificantly (p gt; 0.05) with increasing net weight gains. We also analysed the effect of the SEUROP classification of cattle carcasses and discovered a stronger correlation between the diameter of muscle fibres and meatiness compared to the classification of fatness of the carcasses.